Advances in stem cell technology, such as the isolation and propagation in vitro of human embryonic stem cells (“hES” cells), constitute an important new area of medical research. hES cells have a demonstrated potential to be propagated in the undifferentiated state and then to be induced subsequently to differentiate into any and all of the cell types in the human body, including complex tissues. This has led to the suggestion that many diseases resulting from the dysfunction of cells may be amenable to treatment by the administration of hES-derived cells of various differentiated types (Thomson et al., Science 282:1145-1147 (1998)). Nuclear transfer studies have demonstrated that it is possible to transform a somatic differentiated cell back to a totipotent state, such as that of embryonic stem cells (“ES”) (Cibelli et al., Nature Biotech 16:642-646 (1998)) or embryo-derived (“ED”) cells. The development of technologies to reprogram somatic cells back to a totipotent ES cell state, such as by the transfer of the genome of the somatic cell to an enucleated oocyte and the subsequent culture of the reconstructed embryo to yield ES cells, often referred to as somatic cell nuclear transfer (“SCNT”), offers a method to transplant ES-derived somatic cells with a nuclear genotype of the patient (Lanza et al., Nature Medicine 5:975-977 (1999)). It is expected that such cells and tissues would not be rejected, despite the presence of allogeneic mitochondria (Lanza et al, Nature Biotech 20:689-696, (2002)). Nuclear transfer also allows the rebuilding of telomere repeat length in cells through the reactivation of the telomerase catalytic component in the early embryo (Lanza et al, Science 288:665-669, (2000)). Nevertheless, there remains a need for improvements in methods to reprogram animal cells that increase the frequency of successful and complete reprogramming. There is also a need for reducing the dependence on the availability of human oocytes.
Animals having certain desired traits or characteristics, such as increased weight, milk content, milk production volume, length of lactation interval and disease resistance have long been desired. Traditional breeding processes are capable of producing animals with some specifically desired traits, but these traits are often accompanied by a number of undesired characteristics, and are often too time-consuming, costly and unreliable to develop. Moreover, these processes are completely incapable of allowing a specific animal line from producing gene products, such as desirable protein therapeutics that are otherwise entirely absent from the genetic complement of the species in question (i.e., human or humanized plasma protein or other molecules in bovine milk).
The development of technology capable of generating transgenic animals provides a means for exceptional precision in the production of animals that are engineered to carry specific traits or are designed to express certain proteins or other molecular compounds of therapeutic, scientific or commercial value. That is, transgenic animals are animals that carry the gene(s) of interest that has been deliberately introduced into existing somatic cells and/or germline cells at an early stage of development. As the animals develop and grow the protein product or specific developmental change engineered into the animal becomes apparent, and is present in their genetic complement and that of their offspring.
An additional problem associated with existing stem cell technologies are the ethical considerations of using advanced human embryos to obtain stem cells. Therefore it would be highly beneficial to have cloned embryos available at an early stage to limit ethical concerns.
In summary, this invention solves long outstanding problems with efficiency, ethical dilemmas, and the problem of how to clone embryos without oocytes.